1. The Field of the Invention
The invention generally relates to the field of data transmission in communication networks. More specifically, the invention relates to simultaneous transmission of high-speed data and out-of-band data.
2. Description of the Related Art
Modem day communication is, in large part, accomplished by transmitting and receiving large amounts of digital data. Digital data signals can be used to transmit information such as database information, financial information, personal and business information, and the like. In addition, digital data signals can be used to transmit voice, video, images etc.
Commonly, digital communication is accomplished using a model known as the Open Systems Interconnection (OSI) model. The OSI model defines a framework for accomplishing digital communications with seven layers on clients communicating in a network. These seven layers are understood by those of skill in the art, and include from the highest level to the lowest level: the application layer, the presentation layer, the session layer, the transport layer, the network layer, the data link layer, and the physical layer. At the application layer, data is used in end user processes. Data is packaged by each of the other layers of the OSI model prior to being sent using the physical layer. The physical layer defines how the data is actually sent on the network, such as by electrical signals, light carried on optical fibers, radio signals etc. Thus, at the physical layer, actual voltages, light levels and radio amplitudes or frequencies are defined as having certain logical values.
At the physical layer, one method of communicating digital data involves the use of transceivers. A transceiver includes a signal power source including electronic hardware for transmitting data signals along a physical link such as a copper wire link or fiber-optic link. The signal power source may be a laser, electronic amplifier, radio transmitter and the like. The transceiver may also include a physical layer signal reception element to receive physical layer signals. The physical layer reception element may be a photodiode, an electronic amplifier, a radio receiver, or the like.
The transceiver may include electronic hardware for decoding signals that are sent between clients into data signals, such as binary representations, readable by digital devices or hosts to which the transceiver is connected. The transceiver may also include electronic hardware for encoding signals that are sent between clients from a binary representation to a physical layer level signal that can be transmitted across a physical link. Thus, in one example, a binary representation is converted to one of a modulated electronic signal, a modulated optical signal, a modulated radio signal or another appropriate signal.
Each transceiver is generally passive with respect to other transceivers. This means that a transceiver simply sends and receives digital data that has been converted to a physical layer level signal without extracting or processing the information represented by the digital data. In other words, transceivers do not generally communicate data to one another for the benefit of the transceivers. Instead, the transceivers communicate data to one another for the benefit of the hosts to which the transceivers are connected.
A transceiver may communicate data for the benefit of the transceiver to the connected host device. For example, a transceiver may be configured to generate digital diagnostic information by monitoring the health of the transceiver. The transceiver may then communicate information about the health of the transceiver to its connected host. This communication typically takes place on an I2C or MDIO bus for communicating between integrated circuits. As a transceiver deteriorates due to age, component failure or other reasons, the host may be aware of the deterioration using such communications received from the transceiver.
Digital diagnostics logic (also referred to herein as “digital diagnostics”) may be used to handle various tasks and to generate monitoring and operating data. These task and data may include some of the following:                Setup functions. These generally relate to the required adjustments made on a part-to-part basis in the factory to allow for variations in component characteristics such as laser diode threshold current.        Identification. This refers to general purpose memory, typically EEPROM (electrically erasable and programmable read only memory) or other nonvolatile memory. The memory may be accessible using a serial communication standard, that is used to store various information identifying the transceiver type, capability, serial number, and compatibility with various standards. While not standard, this memory may also store additional information, such as sub-component revisions and factory test data.        Eye safety and general fault detection. These functions are used to identify abnormal and potentially unsafe operating parameters and to report these to the host and/or perform laser shutdown, as appropriate.        Temperature compensation functions. For example, compensating for known temperature variations in key laser characteristics such as slope efficiency.        Monitoring functions. Monitoring various parameters related to the transceiver operating characteristics and environment. Examples of parameters that may be monitored include laser bias current, laser output power, receiver power levels, supply voltage and temperature. Ideally, these parameters are monitored and reported to, or made available to, a host device and thus to the user of the transceiver.        Power on time. The transceiver's control circuitry may keep track of the total number of hours the transceiver has been in the power on state, and report or make this time value available to a host device.        Margining. “Margining” is a mechanism that allows the end user to test the transceiver's performance at a known deviation from ideal operating conditions, generally by scaling the control signals used to drive the transceiver's active components.        Other digital signals. A host device may configure the transceiver so as to make it compatible with various requirements for the polarity and output types of digital inputs and outputs. For instance, digital inputs are used for transmitter disable and rate selection functions while outputs are used to indicate transmitter fault and loss of signal conditions. The configuration values determine the polarity of one or more of the binary input and output signals. In some transceivers, these configuration values can be used to specify the scale of one or more of the digital input or output values, for instance by specifying a scaling factor to be used in conjunction with the digital input or output value.        
The data generated by the digital diagnostics described above is generally only available to the host on which a transceiver is installed. Thus, when troubleshooting problems with individual transceivers, a user must access the host on which the transceiver is installed to discover any digital diagnostic data about a transceiver. This may cause various difficulties when the host and transceiver are located in a remote location such as on the ocean floor or in remote desert locations. Further, some applications make use of repeaters, which are transceiver pairs that simply receive an optical data stream, amplify the optical data stream, and retransmit the optical data stream. In repeater applications, the digital diagnostic data is stored on the repeater. Thus to troubleshoot the repeater, the repeater must be physically retrieved and queried for any digital diagnostic data.
Some protocols exist where digital diagnostic data can be sent as part of the high-speed data sent on an optical link. However, this generally involves sending the data in some specially defined packet or portion of a packet. Thus to retrieve the digital diagnostic data, the high-speed data must be disassembled such as by a framer, the digital diagnostic data extracted, and the high-speed data reassembled. Additionally, if digital diagnostic data is to be added by a transceiver in a chain of transceivers, the high-speed data must be disassembled and the digital diagnostic data added in the appropriate portion of the high-speed data, and the high-speed data, including the digital diagnostic data, reassembled. To disassemble and reassemble a high-speed data signal represents a significant and unwanted cost in terms of data processing. Additionally, there are time delays as the data is disassembled and reassembled prior to retransmission of the data from link to link.
In other presently existing systems, the digital diagnostic data may be sent in a high-speed data signal that includes multiple channels where one of the channels is reserved for high-speed data. This implementation cannot be used in single channel systems. Further, the use of a channel for diagnostic data reduces the amount of other high-speed data that can be transmitted. Also, the cost of disassembling and reassembling the high-speed data signal remains as the channel with the digital diagnostic data must be extracted from the high-speed data signal to obtain the digital diagnostic data and re-added to the high-speed data signal when the high-speed data signal is passed to other links in a network.
Another challenge that arises with transceivers presently in the art relates to negotiating data rates along a channel. Communication at the physical layer includes protocols that specify, among other things, the data rate at which communication may be accomplished. Some protocols have variable communication data rates. This may be useful as the quality of the links between hosts vary. A lower quality link often requires lower data rates to avoid errors. Additionally, data rates may be faster on later produced devices as technology advances. A protocol that allows for different data rates is the fiber channel protocol that supports data rates of 1, 2 and 4 Gigabits/second. Typically, a link between two devices requires that the device communicate at the same data rate. Where devices are capable of communicating at different data rates, the devices, such as host devices, negotiate the data rate at which communications will occur. Presently existing negotiation protocols are complex and may require inordinate amounts of network and computing resources to properly negotiate a data rate.